/**
  1. 指数运算符(幂): **
  2. Array.prototype.includes(value) : 判断数组中是否包含指定value
 */

console.log(3 ** 3)//27
let arr = [1,2,3,4, 'abc']
console.log(arr.includes(2))//true
console.log(arr.includes(5))//false